This invention relates to an apparatus for use in ICP mass analysis.
Traditionally, in an ICP mass spectrometer, the following two kinds of structures have been utilized. In FIG. 2(a) are illustrated structures of a sampling chamber 3 to extract ion from an ion source 1 of ICP and of a vacuum chamber 11 with an ion electrode system 6 and a mass spectrometer 10. The degree of vacuum of the sampling chamber 3 is 1 Torr., and the vacuum degree of the adjacent vacuum chamber 11 is 10.sup.-6 Torr.
In the apparatus shown in FIG. 2(a), that has been traditionally used, in order to increase the vacuum degree of the vacuum chamber 11 which has an ion electrode system 6 and a mass analyzer 10, becomes necessary to provide a vacuum pump with a large exhaust pipe, causing it a drawback that the pump has to be large-sized.
In FIG. 2(b) are illustrated structures of a sampling chamber 3 to extract ion from an ICP ion source 1, a vacuum chamber 7 with an ion electrode system 6 and another vacuum chamber 11 with a mass spectrometer 10. The degrees of vacuum of the sampling chamber 3 and two vacuum chambers 7 and 11 are 1 Torr., 10.sup.-4 Torr., and 10.sup.-6 Torr., respectively.
In the apparatus shown in FIG. 2(b) and disclosed in Literature 1, because the vacuum degree of the vacuum chamber 7 having the ion electrode system 6 is low, it is required to make the ion electrode system multistage in order to prevent ion scattering and to focus ion.
Literature 1: Titled: "Inductively Coupled Plasma Source Mass Spectrometry Using Continuum Flow Ion Extraction" by Messrs. A. L. Gray and A. R. Date (Appeared in Vol. 108, #1033 of Magazine "Analyst" published in 1983.)